1. Field of the Invention
The present invention relates to a technology for resolving a data mismatch between plural database management apparatuses that manage databases having the same contents.
2. Description of the Related Art
Recently, with a rapid increase of capacity of a database, a plurality of database management apparatuses has been used for managing same data so as to improve security and reliability of the database. For example, a pair of a master management apparatus and a replica management apparatus is used for managing the same data. In some cases, the master management apparatus and the replica management apparatus employ same code formats, for example, same character codes and/or same matrix. Alternately, when the master management apparatus and the replica management are used in different systems, each code format for each management apparatus can be unique.
Upon managing the same data using different database management apparatuses, each database management apparatus updates the data for each database. Therefore, although the data in each database are the same in the beginning, there occurs data mismatch between the database management apparatuses with time. Thus, technologies for resolving the data mismatch between the different database management apparatuses have been proposed.
For example, Japanese patent Application Laid-Open No. H7-28684 discloses a technology for resolving the data mismatch between the different database management apparatuses by detecting difference between databases managed by the different database management apparatuses and reflecting the difference in updated data of a database into all the database management apparatuses.
FIG. 13 is a table for explaining the conventional technology. For example, master data (original data) in a 2×2 matrix are copied in replica data (copied data) (see, FIG. 13(1)) and each data is managed in different database management apparatuses. The master data and the replica data are updated respectively in each database management apparatus, such that the master data represented by (B, R1) is updated from 50 to 20, the master data represented by (B, R2) is updated from 300 to 230, the replica data represented by (A, R2) is updated from 200 to 150, and the replica data represented by (B, R1) is updated from 50 to 80 (see, FIG. 13(2)). As described above, because each database management apparatus updates the data for each database, there occurs the data mismatch among the updated data.
To resolve the data mismatch, the updated data in the replica data are primarily used over the master data so that the updated replica data represented by (A, R2)=150 and (B, R1)=80 are reflected to the master data (see, FIG. 13(3)). Thereafter, the updated data in the master data represented by (B, R2)=230 is reflected to the replica data (see, FIG. 13(4)). The master data represented by (B, R1) has already become the same as the replica data because of the data reflection from the replica data to the master data.
As described above, the difference in the updated data of the replica data is firstly reflected to the master data, and thereafter, the difference in the updated data of the master data is reflected to the replica data, resulting in the data mismatch between the master data (original data) and the replica data (copied data) can be resolved.
However, with the conventional technologies, the data mismatch can be resolved only when the database management apparatuses employ the same code formats. Thus, there still is a problem that the data mismatch cannot be resolved if the code formats among the database management apparatuses are different. For example, when a database A employs an extended binary coded decimal interchange code (EBCDIC) for a character code while a database B employs a Shift-JIS code for a character code, the data mismatch between the database A and the database B cannot be resolved due to an occurrence of a failure caused by the different character codes.